Empty Derived Class inherited from Non-Empty Base Class

Question

class Base 
{
   int i ;
};

class Derived : public Base { } ;

int main()
{
   cout << sizeof(Derived);
}

Output :
 4

In Base class , since i is private , it should not be inherited to the Derived Class . Hence , the Base class should act as empty class . And sizeof empty class is 1 , then why it is showing as 4 ?

Why should the `sizeof` an empty class be 1? BTW, it's not empty. — Brian Cain, Sep 25 '13 at 19:23
"...since i is private , it should not be inherited..." - nonsense!!! — valdo, Feb 21 '14 at 18:23
P.S. if you really believe that `i` would not be inherited since its' private, - then why does your `Derived` inherit it in the first place? — valdo, Feb 21 '14 at 18:28

score 4 · Answer 1 · answered Sep 25 '13 at 19:23

4

A Derived class still contains i in Base, it just isn't accessible, so the size 4 is because of i

answered Sep 25 '13 at 19:23

cdmh

3,294
2
26
41

score 0 · Answer 2 · answered Sep 25 '13 at 21:34

0

The size still is 4 because the size of Base is 4. Lets say for example that Base has a function public: int getI() {return i;} then you are able to call Derived::getI(), therefore Derived does need to include the private base members.

answered Sep 25 '13 at 21:34

Georg Bremer

86
4

score -2 · Answer 3 · answered Feb 21 '14 at 18:12

here,derived class is defined publicly.. means here in definition ": public base"

thus derived class can access all public as well as private members of base class..it will make all private members public in that derived class..thus output is 4 coz of i.not 1.if u write private instead then it will give output 1..

Empty Derived Class inherited from Non-Empty Base Class

3 Answers3